Traffic speed deviation computer



March 26, 1963 J. L. BARKER TRAFFIC SPEED nEvIATIoN COMPUTER 4 Sheets-Sheet 1 Eiled Nov. 9, 1959 March 26, 1963 J. L. BARKr-:R 3,082,949

TRAFFIC SPEED DEVIATION COMPUTER Filed Nov. 9, 1959 4 Shets-Sheet 2 |1- cHoPPER SERVO MOTOR SERVO MOTOR AMPLIFIER SERVO AMPLIFI E .R

C HOPPER 68 il# :s INVENTOR. I JoHN BARKER ATTORNEY March 26, 1963 J. l.. BARKER TRAFFIC SPEED DEVIATION COMPUTER 4 Sheets-Sheet 3 Filed NOV. 9, 1959 www# IN VEN TOR.

JOHN L, BARKER 822mm@ ATTORNEY March 26, 1963 J. BARKER 3,082,949

TRAFFIC SPEED DEVIATION COMPUTER Filed Nov. 9, 1959 4 Sheets-Sheet 4 INVENTOR.

JOHN L. BARKER `ATTORNEY United States Patent O 3,082,949 TRAFFIC SPEED DEVIATION COMPUTER John L. Barker, Norwalk, Conn., assigner, by mesne assignments, to Laboratory for Electronics, Inc., Boston, Mass., a corporation of Delaware Filed Nov. 9, 1959, Ser. No. 851,771 20 Claims. (Cl. 23S-151) The present invention relates to a vehicular tralic speed deviation measuring or indicating system or apparatus, which in a general sense measures or responds to the amount or degree of variation between the speeds of individual vehicles of a series of vehicles in traffic proceeding along a road or a traic lane for example, and which in a more particular sense in its preferred aspect computes a deviation representing the average departure of the individual speeds from the mean value of such speeds and provides an output representing the deviation for indicating or control purposes. More specifically in its preferred aspect the present system or apparatus computes the square of the root mean square of the various speeds and also the square of the arithmetic average of the same speeds, subtracts the latter square and takes the square root of the difference Vas an output representing the deviation.

The invention is described herein with particular reference to its preferred application to traiiic speeds but it will be appreciated that some aspects of the computation of the deviation of a series of values in accordance with the invention may have general application to factors other than traic speed.

The invention has particular advantage in determining the deviation in speeds of the latest desired number of vehicles proceeding in the same direction past a sampling point in a single traffic lane. Several deviation computers may be employed respectively in several adjacent traffic lanes if desired, although one such computer in one lane may serve as a sample of multi-lane traffic.

In the rlield of trai-lic control, the speed deviation of vehicle traffic on a roadway may be used as a yardstick of the quality of the traic llow along that roadway. Speed deviation of traic ow along a roadway may also be used as a measure of the efficiency with which vehicle traffic is passed along the roadway, with particular ernphasis on restricted thoroughfares such as freeways, bridges and tunnels for example, and thus may serve as a guide in roadway design and in the monitoring of operation of such tralic facilities for example.

In determining the deviation of varying values of a given factor several mathematical formulas may be employed. Generally referred to as sigma or standard deviation, one mathematical formula is presented at page 165 in Traic Engineering Handbook, second edition, published and copyrighted in 1950 by Institute of Traflic Engineers and Association of Casualty and Surety Companies. Here, referring in particular to speed deviation of vehicle traic, standard deviation is expressed in Drdylg rali.

the formula -where SD means standard deviation and M equals arithmetic average of all observations; X equals value of a single observation;

F equals frequency of observation of one value;

N equals number of observations ice Thus, with relation to vehicle speeds, standard deviation, or sigma or deviation equals the square root of the remainder after the square of the arithmetic average speed (f-?) of a predetermined number of vehicle speeds is subtracted from the summation of the Squared same vehicle speeds divided by the same predetermined number of vehicle speeds, or root mean square speed squared (m2).

Thus the formula may read deviation equals:

#mi or the square root of the difference of the root mean square squared minus the arithmetic average squared.

I have used this formula in the electro-mechanical computation of speed deviation of vehicle traic. In the preferred system the various speed readings are obtained and a speed of the last car value'and a root mean square speed squared value, in the form of D.C, voltages are developed electro-mechanically and are then applied aS individual inputs into the electro-mechanical computer for computation of speed deviation. i

Prior estimates of and mathematical calculation of the raverage speed of vehicle traffic have been made in various manners employing mechanical speed determining and measuring devices and/or electronic calculating devices.

One method of determining the root mean square speed or" vehicle traic through traic actuation, with provision for obtaining an output representing the root mean square speed squared, and an output representing the speed of the last vehicle is taught in my copending application, Serial Number 732,248, filed May l, 1958, under the title Trafiic Monitoring System. Y

From one aspect the present invention provides a vehicle actuated traflic speed deviation indicating system capable of determining and indicating speed deviation currently or on a substantially continuous basis for traffic passing a given location on a roadway or traflic lane.

From another aspect the present invention relates to ynovel apparatus and method for determining the average speed of vehicle traliic on a roadway and for determining and indicating speed deviation of the measured speeds of vehicles in the traflic liow automatically.

My said copending application Serial Number 732,248 describes a vehicle traffic monitoring system for sensing the presence and speed of each vehicle passing a particular location in the roadway, and for indicating each vehicle speed, the root mean lsquare speed of a predetermined number of vehicles and the volume of trac on a roadway.

As more fully described in my said copending application, the presence of a vehicle is sensed and its road speed is evaluated through the cooperation of a radar sensing unit R81 and a speed and volume impulse translator. The detection and speed information of each vehicle so sensed, is available in the forms of electrical output of the speed and volume impulse translator. Detection information is available in the forni of closure of a normally open contact as a vehicle passes under the radar sensing unit while the speed information is available n the form of a D.C. voltage, the amplitude of which is proportional to the speed of the vehicle sensed, with 14 Volts equal to miles per hour, for example.

Each time a vehicle is sensed its speed is read and converted into a D .C. voltage proportional to its road speed at the moment of measurement. This D.C. voltage relierred to as being representative of last car speed, is available as one of the outputs of the speed averaging unit of the said copending application.

Another voltage, representative of the last car speed squared is also developed and several consecutive voltages representative of several consecutive last car speed squared values are averaged by electro-mechanical averaging cir- `cuits to obtain the root mean square speed squared of the last predetermined number of vehicles passing a prede- 'termined position. A D.C. voltage representing the root means square speed squared (R.lvI.S.2) is also available as one of the outputs of the Vspeed averaging unit of my said copending application.

According to the preferred embodiment the D.C. voltage proportional to the last car speed and the D.C. voltage representing the root mean square speed squared are applied to a deviation unit. The deviation unit receives the D.C. voltage proportional to the last car speed and electro-mechanically provides a D.C. voltage output representing the arithmetic average speed squared of the last predetermined number of last car speeds; the output representing the arithmetic average speed squared is based on substantially the same vehicle speeds as the root mean square speed squared output of the speed averaging unit all of these output voltages being referred back to a common reference level.

The D.C. voltage representing the arithmetic average speed squared, Z, is subtracted from the root mean square speed squared, B MSZ, in a difference computer circuit in the deviation unit providing a diierence voltage .representing deviation squared. Through electro-mechanical computation a D.C. voltage is obtained in the 'form of an output which may be used to drive a motor to 'indicate speed deviation on a calibrated scale or such output may be made to operate a circuit at a selected or selectable value of speed deviation.

, It is therefore an-object of the present invention to provide apparatus for use in a traffic monitoring system for 'providing an electrical output representing the root means square of the speeds squared of a last predetermined `number of vehicles passing a predetermined position on a itratc lane or roadway and for providing an electrical output representing the arithmetic average of the speeds squared of the same last predetermined number of vehicles and deriving therefrom speed deviation in the form of an electrical output.

` It is another object to provide a trathc speed deviation 'measuring or indicating system that automatically determines speed deviation of vehicle traic passing a predetermined position on a traic lane or roadway.

' Afurther object is to provide a vehicle actuated trafiic speed deviation indicating system that provides speed deviation of the last predetermined number of vehicles so ac- -tuating the said trahie speed deviation indicating system. It is also an object ofthe invention to provide a deviation unit for cooperation with a speed averaging unit having a last car speed output signal and a squared root mean square output signal, to determine the speed deviation of a desired number of vehicles or cars.

It is further object of the invention to provide an improved deviation computer. Other objects will become more apparent from a reading of the following detailed description with reference to the accompanying drawings where:

'A FIG. 1 represents, in block form, one form of traic speed deviation measuring or indicating system, in accordance with the present invention;

IFIG. 2 represents, partly in block and partly in schematic circuit form, an alternate form of speed averaging unit that may be used as part of a complete trafiic speed deviation computer in accordance with the present invention, and

FIG. 3, including FIG. 3a and FIGfBb, illustrates, in u schematic circuit form the preferred embodiment of the deviation unit.

Referring tovFlG. 1 in more detail, a block diagram of one form of trac speed deviation indicating system is presented including-a vehicle detection and speed sensing unit, that maybe in the form of, the Radar Sensing Unit,

block 10, an associated Speed and Volume Impulse Translator, block 11, a Speed Averaging Unit, broken line block 12 and a Deviation Unit, broken line block 13.

The Radar Sensing Unit may be similar to the Radar Sensing Unit RSI disclosed in my copending application Serial Number 732,248, filed May 1, 1958, under the title Traic Monitoring System which detects the presence of a vehicle on the roadway and thereafter senses its speed giving a composite signal output indicative of vehicle detection and speed combined.

The Speed and Volume Impulse Translator, may be similar to the Speed and Volume Impulse Translator disclosed in my said copending application Number 732,248, which translates the composite output of the Radar Sensing Unit into two separate informations. One output of the Speed and Volume Impulse Translator is in the form of a normally open Contact which closes representing detection of a vehicle and a second output in the form of a D.C. voltage proportional to the speed of a vehicle or speed indication.

The two outputs of the Speed and Volume Impulse Translator are in usable form for input into a Speed Averaging Unit, represented by broken line block 12. Broken line block 12 may represent a Speed Averaging Unit similar to the Speed Averaging Unit described and illustrated in my said copending application Number 732,248 which receives the outputs from a Speed and Volume Impulse Translator and provides therefrom D.C. voltage outputs 4individually representing the speed of the vehicle detected (last car speed) and the root mean square speed squared (R.M.S.2) where a last car speed of 0 to 100 miles per hour is represented by a D.C. voltage of 0 to +110 volts, for example. n

Within broken line block 12 is -a functional block diagram of -a speed averaging unit basically similar to the functional block diagram presented in my said copending Aapplication representing the disclosed Speed Averaging Unit. The present functional block diagram differs from rthe functional block diagram in my said copending application in that a relay, AIN is shown in the Null, block 26; -a relay Ab is shown in Gate, block 24; and broken 'lines 37b and 41 areextended `from the block diagram.

The relay AIN represents that a relay, labeled AIN in the .circuit diagram in my said copending application, is opei'ated by the Null 26 while relay Ab represents that a rel-ay, labeled Ab (along with a parallel connected relay VAa) in the 4circuit diagram in my said copending application, is operated as Gate 24. The broken -line 37b indicates that the Null 26 is used to operate Not Gate 43 and Gate 45 in broken line block 13 and broken line averaging unit that may be used in association with block 13 of FIG. 1 thus providing an alternate form of traic speed direction indicating system. 'Iihe blocks 1U vand 11 inFIG. 2 -are similar to the blocks 10 and 11 in FIG. 1 while the remainder of FIG. 2, the simplified -form of `a speed averaging unit, may be employed to provide out-puts for input into block 13, the deviation unit. The outputs lof the speed averaging unit, 12, of FIG. `1 for input into block 13 tare substantially in the same form as the outputs of the speed averaging unit of FIG. 2. Thus FIG. 1 represents one form of traic speed deviation indicating system while the combination represented in FIG. 2 plus a deviation unit, represented by block 13 in FIG. 1, represents another form of traic speed .deviation indicating system. Y Y V Block 13 represents a deviation unit and is illustrated in full schematic circuit form in FIG. 3 including PIG. 3a and FIG. 3b. t Y

In point of time, the detector impulse output from the speed and volume impulse translator is .applied to the speed averaging unit followed shortly thereafter by the speed indication output. Thus the detector impulse is applied to speed averaging unit where the length of the detector impulse is used to determine the time the detected vehicle will be .at a predetermined position relative to the radar sensing unit. This predetermined position is at a position approximately at a 60 degree angle between the vertical from the sensing unit to the roadway and the line between the sensing unit and the vehicle.

With the detector impulse applied to block 15, Time Delay to 60 Point, and Speed Indication applied to Gate 17 the speed information, in the form of D.C. voltage, is fed via Gate 17, to Calibration Circuit 18, and to L C. Electrical Storage, 19, and at a time as controlled by block 15, Gate 17 is operated via lead 16 to cut olf the voltage applied therethrough.

The speed indication in the form of a D.C. voltage whose amplitude of from 0 to +l4 volts representing 0 to 100 miles per hour, is applied to ya calibration circuit, block 18, which ladjusts the speed indication voltage so that a `scale of 0 to +10 volts equals 0 to 100 miles per hour. rFhis last vehicle speed (LC.) indication of 0 to volts is applied to an LC. electrical storage, block 19. Block 2G, LC. Mechanical Storage, is driven by means of a phase sensitive reversible servo motor to match the value stored in block 19 so that a voltage representative of the speed of the last Vehicle or LC. will be stored both electrically, as for example by `a charge on a capacitor representing L.C. and mechanically, as for example, ?by positioning the arm of a potentiometer so that with a fixed voltage applied through the resistance ofthe potentiometer the voltage at the arm of the potentiometer will be substantially equal to :the value of the charge on the capacitor and thus each voltage value will be representative of the L.C.

The block 20 may include a servo lamplifier [and a servo motor which may be used to position the arm of the potentiometer of the L.C. mechanical storage, typical circuitry of which is fully disclosed in my said copending application Number 732,248.

A squat-ing potentiometer is provided, lblock 21, with the arm of the squaring potentiometer connected to the arm `of the LC. mechanical storage potentiometer so that 4as the arm of the potentiometer in block 26i is driven to match electrical storage, the arm in block 2t? is driven to a corresponding position and an output from block 21 is lobtained representing the last vehicle speed squared or Thus when the gate 17 `operates to cut fofr" the voltage applied through the gate, as controlled by 'time delay 15, the L.C. value in block 19, having been recalibrated by block 18, represents the speed of the last vehicle yand block 29 is driven to match the value of block 19 thus mechanically storing the LC. speed while block 21 is driven with block 20 to provide an output representing the square of the last vehicle speed or EE?.

The output of `block 21, EE?, is `applied to `a block 22, Number of Cars Averaged Circuit. Block 22 may, for example, include a voltage divider which may be adjustable so that the number of car speeds averaged may be adjustable, as desired. Also -applied to the block 22 via lead 31, is the output voltage of block 29, a volt-age representing the old root mean square speed squared (Ril-5.2) so :that the last vehicle speed squared may be averaged with the root mean square speed squared and a new root mean square speed squared may be applied to New R.M.S.Z Electrical Storage, block 23.

As block 2t) and block 21 are being adjusted to a new value the electrical storage in block 23 is being adjusted to a new value also.

When the value of the output of block 20 or the LC. mechanical storage equals the value of the output of block 19, or the L C. electrical storage, a null (block 26) between the two outputs is reached which operates a relay, here indicated as relay AIN. A gate block 24 including a second relay, here indicated as relay Ab, is operated by null, 26 via lead 25 and 37a. At this moment since the block 21 has also been adjusted to a new C? value, the block 23 has been adjusted to a new RMS.2 electrical storage value.

Operation of the gate, block 24, via lead 37a from the block 26, permits adjustment of the RMS? Mechanical Storage, block 29.

The block 23, new R,M.S.2 electrical storage may, for example, include a capacitor capable of storing and holding an electrical charge representative of the RlVLS.Z while the block 29, RMS? mechanical storage may, for example, be in the form of a lpotentiometer with an arm adjustable through a servo mechanism so that the value of the voltage output at the arm of the potentiometer may be adjusted to equal the value of the voltage charge on a capacitor in block 23.

The block 20 and the block 29 may, for example, each include a servo amplifier section and a phase sensitive, bidirectional servo motor which may be employed to drive the movable arms of the respective potentiometers to a position where the output of the respective blocks, which is the voltage at the respective arm of the potentiometer, is equal to the input from the previous block or one servo amplifier may be employed and switched as desired between the servo motors of the respective blocks as illustrated in my said copending application Ntunber 732,248.

Upon reaching a null between the output of block 23 through gate 24 and the output of block 29, the null, block 30, for example, may operate to open this circuit at gate 24 and reset the mechanism preparatory for receipt of the next succeeding detector impulse and speed indication.

Thus out of the block 12 an output representing the speed of the last vehicle (L.C.) 35, is obtained from block Z6 and an output representing the root mean square speed squared (RJNLSP) 36, is obtained from block 29 with both outputs applied to block 13, the deviation unit as here illustrated.

Last vehicle speed information (L.C.), lead 35, is applied to Number of Cars Averaged Circuit, 4tl lin the deviation unit7 broken line block 13. Broken line 41 between block 22 and block 40 is to indicate that both number of cars averaged circuits are adjusted to select the same numbers of cars to be averaged. Also applied to block 40 is a voltage from Arithmetic Average Speed Mechanical Storage, block 46, via lead y42, representing the old Arithmetic Average Speed from the mechanical storage. Thus the speed of the last vehicle, LC. via lead 35, is applied to the number of cars averaged circuit 40 and is averaged with the old arithmetic average speed and applied through Not gate 43 to block 44 the new Arithmetic Average Speed Electrical Storage (A.A.).

It should be observed that the not gate 43 and gate 45 are both connected, by broken line 37b and lead 2S to null, block 26. Not gate 43 is the inverse of gate 45, that is, although both gates are operated simultaneously via lead 37b, not gate 43 is closed when gate 45 is open and vice versa.

Concurrently as block 2&3 L.C. mechanical storage, is being adjusted, prior to operation of the null relay AIN, the L.C. information is being fed via lead 35 to block 43, through block 43 and into block 44 so that block 44 is being adjusted to a new value through not gate 43 before the null occurs between blocks 19' and 20;

When the null between blocks 19 and 2d occurs operation of null relay, AIN, reverses the condition of the gate 4S so that block 46 may be adjusted to the new value now on block 44 and also reverses the condition of the not gate 43 so as to stop further adjustment of block 44 from block 40.

The new Arithmetic Average Speed Electrical Storage data is now transferred' to the Arithmetic Average Speed MechanicalV Storage through closure of gate 45. Thus the A.A. mechanical storage, block 46 is driven to watch the value of the new A.A. electrical storage block 44 at substantially the same time as RMS? mechanical storage block 29, is driven to match new M.R.S.2 electrical storage block 23.

The Arithmetic Average Speed Squared, ET-.2, block 47 is linked to block' 46 so that as the arm of the potentiometer in block 46 is adjusted to a new position the arm of the potentiometer blocked block 47 is also adjusted to a new position relative to the position of the arm in block 46.

As illustrated in the circuit form partly in FIG. 3a and partly in FIG. 3b block off by broken line block 46, the block 46 in FIG. l may include a chopper coupled to a servo amplier which drives a servo motor and a potentiometer with the arm of the potentiometer mechanically connected, 'through suitable gearing, to the servo motor, which is illustrated as a phase sensitive, bidirectional motor.

The output of block 47, a voltage representing the arithmetic average speed squared i7@ is fed via lead 47a to block 48, a difference computer.

The output R.M.S.2 of block 2.9 of the speed average unit, 12, is also applied via lead 36 to the deviation unit, 13, into block 48 so that the RMS?, in the orm of a voltage representing the root mean square speed squared, which is on the same base as the KIZ, and the 'TZ may be subtracted from each other so that the difference voltage may be obtained, which represents speed deviation squared, which may be mechanically stored in block 49. Block 49 in FIG. l may include a chopper coupled to a high gain servo ampliier assembly, which drives a servo motor and a potentiometer, the arm of which is mechanically connected, through suitable gearing to a phase sensitive, bidirectional motor, as illustrated partly in FIG. 3a and partly in FIG. 3b block oft by broken line block 49.

Block '50 may include la potentiometer, the arm of which is linked :to the arm of a second potentiometer, 'in block 49 so that the arm in block 50 is positioned on its associated resistance corresponding rto the position of the arm in y.block 49 on its associated resistance with the output of the larm in block 50 applied to the resistance of the potentiometer in block 49. Thus `as the output of block 49 represents deviation squared, the output of block 50 is a voltage representing the square root of fthe deviation squared and thus the value of the output at lead 50a is the trafc speed Ideviation which may be displayed on a meter suitably connected to the output as for example meter 232 in FIG. 3b.

FIG. 2 illustrates, pantly in block and partly in scher vmatic forma simplified form of speed averaging unit that may be used in yassoci-ation with the deviation unit to form a tralhc speed deviation indicating system.

The speed yaveraging unit illustrated in FIG. 2 differs somewhat 4from the speed averaging unit disclosed in my said copending application Number 732,248 although the radar sensing unit, (R.S.'U.), .10, may bev similar to the radar sensing unit R.S.'I. described in my said copending application and previously mentioned herein, .and the speed and volume impulse translator (S.V.I.T.), 11 may be similar to the speed and volume impulse translator described in my said copending application and previously mentioned herein.

The composite signal output of the radar sensing unit, 'block 10, will -be fed to Ythe speed and volume impulse translator, block 11, as a vehicle passes under Vthe radar sensing unit. The composite signal is translated into a 'detector impulse which operates a relay 170, to close a pair of normally open contacts A, in block 11, for example, and into speed indication as a D.C. output via 8 lead 88 of 0 to +14 volts D.C. representing 0 to 100 miles per hour. The speed indication signal is applied to a potentiometer 60 and arm 61 picks ol a percentage of the signal.

Since the vehicle speed will be measured atan angular position of approximately 60, between the vertical, :from the sensing unit to the roadway and line between the sensing unit and the vehicle, and since the vehicles speed as stored on capacitor 64 should `be calibrated 0 to +10 volts equal lto 0 to 100 miles per hour speed; the setting of arm 6l Iis such as to compensate for the angular position of the vehicle at the time contact T1 opens the circuit, as will be described later.

Although yan angular position of 60 is the preferred posi-tion such angular position is not limited to 60 as the arm 61 may -be positioned for recalibration of speed taken at other angular positions as desired.

Thus the signal applied via lead 88 is recalibrated before being applied through diode 62 and contact T1 to capacitor 64. Capacitor `64 may -be called a last car speed electrical storage since with contact T1 of relay T closed, the voltage picked off at arm 61, which represents the speed of the last car, is applied to and does charge capacitor 64 to such voltage. The resistance `63 provides a bleed oit path so that capacitor 64 may discharge somewhat if the speed indication of the previous vehicle was higher than the speed indication of the present vehicle thus providing -for controlled charge and discharge to assure that the charge placed on the capacitor 64 is substantially equal to the voltage at arm' 61 which represents the speed =of the vehicle.

Operation of fthe speed averaging unit `ol? FIG. 2 commences with energization of the relay resulting in closure of contact A. The detector impulse, which is inversely proportional to the speed of the vehicle sensed maintains the relay 179 energized -for such time period.

Closure of contact A of relay 170 in block 11 cornpletes a pull-in circuit for relay R from a common ground through contact A, normally closed contact S1 of deenergized relay S, the coil of relay R to D.C. supply.

Relay R closes its contacts R1, R2 and R4 thus completing a holding circuit through contacts A, and R1.

The opening of contact R3 and closure of R2 opens the charging circuit -for capacitor CT and provides a bleed off path through 4adjustable resistor S11, lafter having been charged from a D.C. supply, vthrough adjustable resistor 52, and contact R3. As soon as the charge on capacitor CT reduces somewhat 'the relay T pulls in from D.C. supply through the coil of relay T, contact R2, `adjustable resistor 51 to ground.

The relay S, upon energization, via contact R4 opens its contact S1 and closes its contacts S2 and S3. Closure of contact S2 provides a holding circuit for relay S from DC. supply, Contact S2, normaly closed contact V4 of relay V to ground. v

Closure of contact S3 completes a pull-in circuit for relay V but relay V is a delay act-ion relay, the delay being on pull-in so that before the end of the delayed pull-in period, energized relay T :opens its contacts T2 thus breaking the pull-in circuit of delayed relay V.

Energized relay T closes its contacts T1 to permit capacitor 64 to assume the potential at Aarm 61 on potentiometer 69.

At termination of the detector impulse by lthe speed and volume impulse translator, the relay 170 becomes deenergized and its contact A opens thus opening the holding circuit for relay R. Deenergized relay R releases and opens its contacts R1, R2, and R4 and closes its contact R3. y l

Relay R cannot now pull-in again so long as relay S remains energized since contact S1, in ythe pull-in circuit 'lof relay R, is heldopen vby now energized Vrelay-S. This prevents any succeeding false operations of contact A =due to a succeeding salient reliec'tion on a long vehicle or an impulse from an exceedingly close spaced second vehicle from getting into the sequence of speed averaging until the first measurement is assimilated in the averaging unit, as herein described.

The period of energization -of relay R is substantially equal to the period of closure tof contact A, which periods fare both inversely proportional to the speed of the vehicle detected. The length of the period :of energization of relay R determines the -amount of discharge of timing capacitor CT -through timing resistance. The amount of discharge of capacitor CT determines the amount of time necessary for controlled recharging of the capacitor. The amount of time necessary for recharging of capacitor CT determines the time `delay between the opening of the energizing circuit for relay T and the fall out of relay T.

Thus the speed of the vehicle as it passes under the sensing unit is utilized to determine when the vehicle will be in a certain desired position with relation to the sensing unit. Since the detector impulse is inversely proportional to vehicle speed, a slow moving vehicle will provide a longer detector impulse and hold relay R energized for a longer period of time thus providing for greater discharge of capacitor CT and longer delayed fall out of relay T than a more rapid moving vehicle. Thus the slower moving vehicle is given more time to arrive at a desired position, than a more rapid moving vehicle is given to arrive at the same position.

When relay R becomes deenergized, at the end of the detector impulse, contact R3 is closed and provides a circuit to charge capacitor CT from D.C. supply, through resistor 52, Contact R3 to capacitor CT to ground while capacitor CT is also being charged from D.C. supply through the coil of relay T to capacitor CT to ground. When contact R3 is first closed, after being held open by relay R, the voltage across relay T will be suicieut to maintain relay T energized although the energizing circuit or relay T has been opened. When the charge on capacitor CT increases to sucient value so that the voltage across relay T can no longer maintain the relay energized, relay T drops out and reverses its contacts, contact T1 becoming open and contact T2 becoming closed.

Upon closure of contact T2 the pull in circuit for relay V is completed from D.C. supply through the coil of relay V, contact T2, contact S3, conta-ct X3 to ground, and,

after a short delay the relay V pulls in and opens its contacts V1, and V4 and closes its contacts V2, and V3.

Closure of contact V3 provides a holding circuit for relay V while closure of contact V2 provides a bleed olf circuit through adjustable resistor 54 lfor capacitor CW, which capacitor became fully charged from D.C. supply through the adjustable resistor 53, contact V1 to capacitor CW and from D C. supply through the coil of relay W to capacitor `CW with capacitor CW returned to ground.

. With capacitor CW discharged somewhat relay W becomes energized and opens its contact W1 to open the ground connection to the servo ampli-tier of block 90 and closes contact W2 thus connecting the chopper, block 68 to the servo amplier through coupling capacitor 69. The chopper, block 63 may be similar tothe chopper, block 68a and each may be similar to the chopper schematically f illustrated in FIG. 3a blocked off by a broken dotted line block labeled 68. The servo amplier, block 9@ may be similar to the servo amplifier block 90a and each may be similar to the servo amplier schematically illustrated in FIG. -3a blocked off by a broken dotted line block, labeled 90' except the servo amplifier in block 90 and 90a do not have their respective outputs shorted out as illustrated in FIG. 3a at junction 1431, via contact 45a.

With the opening of contact T1 the charge on capacitor 64 remains and such charge is applied tothe grid 65 of cathode follower 66.

The amount oli power drawn by cathode follower 66 is proportional to the potential applied to grid 65. so that the voltage on lead 67, which is a fixed percent of the power drawn by the cathode follower 66, is proportional 10 to the potential on grid 65 which is equal to the charge on capacitor 64 which charge represents the speed of the last vehicle.

T he voltage on lead 67 is applied .to a chopper, block 68 and such voltage is employed as a reference to which a voltage on lead 70 may be adjusted by oepration of a two phase bi-directional servo motor, block 91 which is connected through suitable gearing to the arm 71 of potentiometer 7 1/ 72.

`With +10 volts D.C. applied through resistor 72, the voltage at arm 7'1 will be a fraction of the -f-"vlO volts according to the position of the arm 71 relative to the extremes ofthe resistor 72. For example, with the arm 71 at a point three quarters of the way up from the bottom of the resistor, a voltage of 7.5 volts which is three quarters of the total applied voltage, will be applied at arrn 71. When the voltages on leads 70 and 67 are unequal this difference is sensed by the chopper 68 and the difference voltage is passed by capacitor 69 in the form of an alternating current (AiC.) to the servo amplifier, via contact W2. The relation between the two voltages, on leads 67 and 70, is expressed in the phase o the A.C. passed by capacitor 69. The relationship of the phase of .the A.C. passed by capacitor 69 with reference to the A.C. operating the chopper and the servo motor, block 91, which is substantially the same A.C., determines the direction of rotation of the servo motor resulting in repositioning of arm 71 of potentiometer 71/72. The servo motor, block 91 is substantially the same as servo motor, block 91a and both may be similar to the servo motor illustrated in FIG. 3b blocked of in broken line 91. As explained below this motor may be a two phase, bi-directional motor.

Thus the arm 71 will be driven to a position on resistvance 72 through which is applied a 10 volt D.C., so that the voltage at arm 71 which is applied to the chopper 68 via lead 70 will be equal to the voltage applied to chopper 69 via lead 67.

With the two applied voltages, via leads 67 and 70 substantially equal there will be no output from the chopper and therefore will be no input into the servo amplier all as described and illustrated in FIG. 3.

The Voltage at arm 71 is applied through the resistor 74 of potentiometer 73/74 and the arm 73- may be linked mechanically to the arm 71 so that as arm 7-1 is positioned on resistor 72 the arm 73 is positioned on resistor 74 relative to the position'of arm 71 on resistance 72?. n Thus the potentiometer 73/ 74 may be referred to as a `squaring potentiometer since the fraction of the ratio between the total applied voltage (+10 v.) and the voltage at arm 73` will be thesquare oli the fractional position of the arm 71 on the resistor 72..

Thusthe voltage at arm 71, since the arm will be driven to a position where the voltage at arm 71. will equal the voltage at lead 6.7, which will equal the charge on capacitor 64, will represent the speed o the last vehicle or LC. `Since the voltage of arm 71 represents the speed of the last vehicle then the voltage at arm 73- may represent the speed of the last vehicle squared or m2.

The output via lead 35 represents the last vehicle speed or LiC. and is in substantially the same form as the output represented by lead 35 in ythe block diagram in FIG. l.

The `voltage at arm 73, representing the last vehicle speed squared (ETC-.2) is fed through resistor 75 to junction 76. Also applied to junction 76 is a voltage from arm 7.9 of potentiometer 79/80l through lead 78, adjustable resistance 77 to the junction 76'. The voltage on arm 79 corresponds to the old root mean square speed squared of the last predetermined number of vehicles excluding the present last car speed all as described below. The resistors 75 and 77 and junction 76 form a voltage divider at junction 76. Depending upon the ratio between the value of the resistances 75 and 77 and the value of the voltages applied at arms 73 and 79 respectively a voltage is applied via junction 76, contact X1 to the capacitor 85 Y 1l t equal to the new root mean square speed squared (Rl/1.5.2) of the last predetermined number of vehicle speeds sensed, including the present last car speed.

When the relay W became energized, contact W4 was opened and contact W3 was closed. 'This provides a controlled bleed ott circuit for the capacitor CX to thereupon energize relay X after a time delay. The delay on relay X pull in, after energiza-tion ot relay W may be somewhat less than one second, for example, to allow suicient time for the repositioning of arm 71 and thus the repositioning of arm 73` and the adjustment of the charge on capacitor 8S before relay X pulls in.

When relay X pulls in from the D.C. supply through the coil of relay.X contacts W3, adjustable resistance 55 y to ground, contact X1 is opened and contact X2 is closed. Contact X3 in the holding circuit of relay V is also opened.

With contact X3 open relay V becomes deenergized and opens its contacts V2 and V3V and closes contacts V1 and V4. Closure of contact V1 provides for controlling charging of capacitor CW to time a delayed fallout of relay W.

The delayed fallout of relay W ensures that sutiicient time has occurred to reposition the arm 71 so that the voltage at arm 71 via lead 70 and the voltage via lead 67 have been adjusted so that the voltages are substantially equal.

Upon deenergization of relay W contacts W2 and W3 open and contacts W1 and W4 close. Closure of contact W4 provides for controlled charging of capacitor CX to time a delayed fallout of relay X.

During energization of relay X contact X2 is closed and the voltage charge on capacitor 85 is applied to the lchopper, 68a, which compares the voltage at arm 79 of potentiometer 79/80, which is fed via lead 78 to chopper 68a, with the voltage charge on capacitor 85. Any difference in voltage is sensed and is passed by capacitor 69a, as an A.C. to the servo amplifier, 90a, which in turn 'ampliies the A.C. and feeds the servo motor 91a. The servo motor 91a is driven according to the phase of the A.C. passed by capacitor 69a with reference to the A.C. operating the chopper 68a and the motor 91a. The arm 79 of potentiometer 719/80 is driven to a positon on resistor 80 where the voltage at arm 79 is substantially equal to the voltage lcharge: on capacitor 85 and both voltages represent the root means square speed squared (R.lvI.S.2) of the last predetermined number of vehicle speeds.

When both voltages applied to chopper 68a are substantially equal there is no input into the servo ampliiier land the motor stops operating.

"Ilhus the arm 79 has been repositioned so that the voltage on arm- 79 is substantially the same as the charge on capacitor 85.

The dual potentiometer arrangement 81/82 and 79/ 80 is similar to the dual potentiometer arrangement 71/72 and 73/ 74. A D C. voltage of +10 volts is applied to Aresistor 82 of potentiometer 81/82 and the arm Slis positioned mechanically on the resistor 82 corresponding to the position of arm 79 on its resistor 80. The Voltage at arm 81, which is a fraction of the applied `+10 volts, the fraction being equal to the position of the arm 811 interum the ends of the resistor 82, is applied to resistor 80 and the voltage at arm 79, which is in a corresponding me- -ohanical position on resistor 80, may be considered the square of the voltage at arm 81, as a fraction of the total.

Thus the potentiometer 79/80 may be referred to as a squaring potentiometer since the fraction of the radio between the total applied voltage (+10 v.) and the voltage at arm 79 will be the square of the fractional position of `the arm 81 on the resistor 82.

Thus the output of arm 79 via lead 3:6 is a D.C. voltage that represents the R.M.S.2 speed and is substantially equal to the charge on capacitor 85.

When the Vrelay X becomes deenergized the relay sequence terminates and the speed averaging unit returns to rest.

Thus it has been described that a D.C. voltage output on lead 35, representing the speed of the last vehicle and a D.C. voltage output on lead 36, representing the root mean square speed squared may be obtained in a manner somewhat different than that described in my said copending application Number 732,248 and these outputs may 'be applied .to the deviation unit, described below to provide an alternate form of traic speed deviation system, the present invention herein.

=It should be noted that the pull-in circuit for the relay R includes a break contact of relay S so that if relay S is energized relay R cannot again be energized if the relay R had previously become deenergized as by termination of the detector impulse.

It should also be noted that due to the sequential operation of the relay assembly a second detector impulse may cause energization of the relay R and initiate a second cycle of operation prior to the complete termination of the original cycle without interfering With normal completion of the cycle then in progress.

rrrIhus a simplified form of speed averaging unit, employing a timed sequential relay operation has been described from which unitris obtained the speed of the last car in a D.C. voltage based on 0 to +10 volts representing 0 to miles per hour and a voltage representing the R.M.S.2 speed for a predetermined number of last vehicle speeds through outputs 35 and 36 respectively.

It, for example, a traic speed deviation system would include a speed averaging unit similar to that just described with reference to FIG. 2 the relay DX of the kdeviation unit, illustrated in FIG. 3a may be energized the same time relay X is energized and could be connected so that the coil of relay X and the coil of relay DX are connected in parallel or may be connected so that the energizing circuit of relay DX includes a make contact of relay X. The latter proposed circuitry may include a source of power, as for example a D.C. supply, connected to one side of a make contact, as contact X4 in phantom form, for example, the other side of contact X4 connected to one side of the coil of relay DX (of FIG. 3a) and the other side of the coil relay DX returned to a common ground.

Operation of the deviation unit, schematically illustrated in its preferred form in FIG. 3a and FIG. 3b, will now be explained relative to its operation in a tratic speed deviation indicating system.

Because of the size and complex circuitry of the deviation unit the circuit drawing includes two figures, FIG. 3a and FIG. 3b. Certain leads interconnect between FIG. A3a and FIG. 3b and these leads are identically labeled and extend to the edge of the respective drawings thus indicating they are interconnected between the gures to a lead identically labeled.

The power supply for the deviaton unit, in FIG. 3 is generally represented by a triangle, in FIG. y3b representing +300 volts D.C. for example; a circle labeled +10 representing +10 volts D.C. for example; a plus in a square representing volts D.C., for example; a minus in a circle representing -10 volts D C. for example, and two closed circles labeled and A.C., representing a 60 cycle per second 120 volt A.C. source, for example.

. Speed information, such as the speed of the last vehicle (LC.) and the root mean square speed squared, (m2) in the form of D.C. voltages similar to the voltages developed and applied as outputs of the speed averaging unit of my said copending application Number ,732,248 and in tbe form of speed averaging unit illustrated in FIG. 2 herein are illustrated as being applied to the deviation unit via leads 35 and 36 respectively in FIGS. 3b and 3a respectively.

Coordination of operation between the speed averaging unit and the deviation unit is obtained through controlled operation of the relay DX, illustrated in FIG. 3a, by the speed averaging unit. Normally relay DX is maintained 'servo motor to erroneous settings.

deenergized with both its contacts 43a and 45a closed.

Last car speed information, in the form of a D.C- voltage with to +10 volts representing 0 to 100 miles per hour speed, is applied through lead 35, FIG. 3b, resistance 102 to a junction 103. This last car speed signal applied to junction 103 is modied somewhat by action of a voltage divider including adjustable resistance 120 and associated resistance 122 and the resistance 102 connected to junction 103, as more fully described below. With contact 43a closed, this modified signal is applied via lead 104 to FIG. 3a Via contact 43a, lead 105 to the 'storage capacitor 44a, which represents the new arithmetic average speed electrical storage.

The contact 45a supplies a ground connection to -a junction 101 in the servo amplifier and effectively grounds any signal that may be applied to the junction 101. This prevents the servo amplifier from floating and prevents Yamplified electrical noise from being applied to drive the This is one method of control that may be used, other methods well known to those skilled in the art, may be used for control of the servo amplier.

The broken line box '43 and the broken line box 45 in FIG. 3a illustrates one type of not gate and gate respectively that may be found in the block diagram in blocks 43 and y45 respectively in FIG. 1.

The broken line box 44 in FIG. 3a illustrates one type electrical storage such as may be found in the block diagram in block 44 in FIG. l. The charge on the capacitor 44a is applied through resistance 106 to contact 107 of chopper 108.

The broken line box 48 includes circuitry that may be included in block 48 in FIG. 1 while broken line box 49 in FIG. 3a includes part of the circuitry that may be included in block 49 in FIG. 1. The remainder of the circuit components included in block 49 in FIG. 1 may be vseen inbroken line box 49 in FIG. 3b.

The broken line box 46 in FIG. 3a includes part of the circuitry that may be included in block 46 in FIG. 1 while the remainder ofthe circuit components included in block 46 in FIG. l are illustrated in broken line box 46 Ain PIG. 3b.

Broken lines boxes 47 and 50, in FIG. 3b, include circuitry that may be included in block 47 and 50 respectively in FIG. 1 While the lead labeled (42) in FIG. 3b,

between broken line boxes 47 and 40 may illustrate the lead 42 in block form FIG. 1. Broken line box 40, in FIG. 3b includes circuitry that may be included in block .4o in FIG. 1.

yIn FIG. 3b, at terminal 160, a +10 volt D.C. supply is applied through resistance 114 of potentiometer 114/115. The value of the D.C. Voltage at arm 115, with respect to ground, is substantially the same as the value of the voltage at junction 110, with respect to ground.

. The voltage at junction 110 is applied via lead (42) through part of the voltage divider including resistance 122, part of adjustable resistance 120 to selector arm 121 to junction 103. Also applied to junction 103 through resistance 102 is a voltage representing the last car speed `via lead 35. The resultant voltage of the voltage divider action is applied via lead 104, to FIG. 3a, contact 43a,

Vrepresents the old arithmetic avenage speed while the voltage potential on contact 107 of chopper 108 represents the new arithmetic average speed; that is the voltage at an A.C. voltage whose amplitude is equal to the difference between :the potentials applied to contacts 107 and 109 and whose electrical phase is determined by the relationship between the two different potentials.

When the voltage potentials at contacts i107 and 109 are substantially *the same, the difference voltage will be zero and without change in potential applied to capacitor 113. Thus capacitor 113 senses a D.C. potenti-al which is substantially lblocked.

The .amplitude of the A.C. volt-age substantially equals any `dii-ference kbetween the two potentials Iat 107 and 109. The electrical phase of the difference potential appearing as an A.C., is determined by the relationship between the two potentials with respect to the Ihigher of the two potentials. 'Thus the electrical phase of the A.C. is determined -by whichever is the higher potential and thus determines the direction in which the arm 115 must be driven on the resistance 114 iso that the voltage at arm 115 or Icontact 109 is made Ito be substantially equal to Vsubstantially 4the same source of A.C. or may be separate sources of A C. but substantially in phase with each other, and are used as a reference to determine the electrical phase of the A.C. passed by the capacitor 113, 13S and 166, as described below.

Let it be assumed, for example, that arm 111 connects with contact 109 I and then with contact 107. Let it also be assumed that the potential at contact 109 is a greater positive value than the potential at contact 107. Under such conditions the wave form a may represent the A.C. wave passed by capacitor 113. This condition may indicate that the voltage at arm 115 must be reduced to equal the potential Iat capacitor 44a and therefore that arm 115 must be repositioned to la lower position on resistance 114 of potentiometer 114/115.

It on the other .hand the value at contacts 107 and 109 were reversed, that is that lthe potential at contact 109 were of a less positive value than the potenti-al at contact 107 then the wave form b may represent the A.C. wave passed by capacitor 113. This condition may indicate that the voltage at arm 115 must lbe increased to equal the potential at capacitor 44a and therefore that the arm 115 must be repositi-oned to a higher position on resistance 114 of potentiometer 114/115.

Thus the phase of the A.C. passed through capacitor 113, with respect to the phase. ofthe reference A.C. is employed to drive the motor in the desired direction to reposition the arm to a position Where the potential at the rar-m 115 is substantially equal to the potential on capacitor 44a.

Returning momentarily to FIG. l, it should be understood that when the voutput ot block 19, which is the last car speed electrical storage, diters lfrom the output of block 20, the last car speed mechanical storage, the null 26, fed 'by both outputs, is not attained. As Iblock 20 is being adjusted so that its output will be equal to the loutput of block l19 (prior t-o attaining the'null) the output v age. 'lihus as block 20 is being adjusted to a. new value the block 44 is also being adjusted to a new value which equals the value of the out-put of block somewhat ymodified by block 40.

When the outputs of block 19 and block 20 are substantially equal a null between the two outputs is attained. At this moment the output of block 20 represents the speed of the last car (L.C.), `and this output has, via flead 35, been applied to and m'odied by the deviation buit so that the output of block 44 now represents a new arithmetic laverage speed (A.A.).

With the occurrence of the null between the outputs of blocks 19 and 20 a relay, for example AIN, shown in block 26 is operated.

Generally, the relay AIN, may con-trol the pull-in circuit for -a relay Ab, tor example, shown in gate, block 24, after which the relay Ab holds through its own contacts.

The coil of relay DX, shown in FIG. 3d, may be connected in parallel with the coil of relay Ab` so that as relay Ab is energized relay DX is also energized.

Thus the relays Ab and DX may -be controlled by relay AIN for initial energization but each .thereafter hold through contacts of relay Ab, independent of relay AIN.

Relay DX, as shown in FIG. 3a controls two sets of contacts. rIlhe block 43 represents one set of contacts while the block 45 represents the second set of contacts.

With relay DX deenergized, that is prior to reaching -a null between blocks 19 rand 20, the contact in -block 43 is closed to permit passage of the L.C. signal from lead 35 through block 40, through gate 43 to block 44, for Vadjustment of the new A.A., while the contacts in block 45 are closed to complete a ground connection to short out Vthe output of the servo amplifier and, in etect nullify the elr'eet of the servo iampliiier on the servo motor.

When the null is attained the relay AIN is operated to operate relay Ab and DX. With relay DX energized not gate 43 is opened to stop charging or adjusting of block 44 and gate 45 is opened to permit adjustment of Vblock 46 breaking or opening the connection to ground thus permitting the servo amplilier to apply its output to the servo motor and thus drive block 46 to a new position according to the value ot block 44.

Thus it may be seen that although the not gate 43 and gate 45 both are illustrated in FIG. 3a as break contacts on relay DX the functional operation of the two gates are opposite to each other.

Returning to FIG. 3, with a diierence signal between the values applied to the contacts 107 and 109 of chopper 108 the varying potential ,on moving arm 111 is passed through capacitor 113 as an A.C. This A.C. signal is applied through resistance 123 to ground.

The A.C. potential is applied to grid 124 of tube 125,` the tube 125 being of the conventional triode type gen# erally employed for ampliiication. The plate circuit of tube 125 is coupled through resistance/capacitance coupling to the grid of a second stage of amplification, in

cluding tube 126. The ampliiied A.C. signal is passed through coupling capacitor 127 to junction 101 andlwhen contact 45 is open, the signal is applied through coil 128 to ground. The A.C. signal applied to coil 128 causes induced current in coil 129 of transformer 128/ 129.

The induced A.C.,potential in coil 129 is applied to the grids 130 and 136 causing alternate conduction of the associated tubes 133 and 137 respectively so that when tube 133 is conducting tube 137 is non-conducting.

The plate circuit of tube 133 follows via lead 138 to FIG. 3b to lead 139 to the lower tap on coil 140 ot servo -rnotor 144. The center tap of coil 140 is connected to `B-lvoltage of the order of +300 volts D.C'. for example. The cathode 134 of tube 133 is connected to lground through cathode load resistance 135.

The tubes 133 and 137 are illustrated as beam power ,tubes connected for push-pull amplication.

The plate circuit of tube L37 follows via lead 145 to phase with the 60 cycle per second A.C. source operating the chopper 108.

The servo-motor 144 represents a phase sensitive, two phase motor which rotates clockwise or counterclockwise according to the phase relation of the electrical current in coil 140 with respect to the electrical phase of the reference electrical current in coil 148. These currents are normally displaced degrees in phase with respect to each other and since the coil 148 is connected across the A.C. line the 90 degree displacement is secured on the other coil 140, through the combination of the capacitor connected across it, the tuning capacitor associated with windings 128 and 129 of the coupling transformer, and through the mechanical phase lag of the armature 111 with respect to its driving coil in chopper 108 which is driven from an A.C. essentially in phase with the A.C. across coil 148.

An indicator lamp L1 which is connected across coil y140 is illuminated when the motor 144 is operating.

Thus according to the phase relationship of the signal passed through capacitor 113, relative to the phase of the A.C. operating the chopper 108 the phase sensitive servo motor 144 is driven clockwise or counterclockwise to reposition the arm L15 until the voltage at arm 115, applied through junction 1410, lead 116, impedance 117 and resistance 118, to contact 109 is substantially equal to the voltage applied to contact 107 from capacitor 44a.

When the two potentials are substantially equal the output of the chopper is substantially zero, thus the signal on grid 124 is reduced to substantially zero.

Now the new arithmetic average speed value is stored on the potentiometer -114/115 with the new value represented by the voltage at arm 115.

The arm is mechanically connected to the motor 144 by suitable gearing and is driven in the desired direction according to the electrical phase relationship between the current in the coils and 148. The arm 15-1 Y as previously described and also applied to the resistance 152 of potentiometer 151/152. The'arm 151 is positioned on resistance 152 according to the position of arm 115 relative to resistance 114, as previously described and the voltage at arm 151 is equal to the square of the fractional position of arm 115 on the resistance 114.

For example, with F10 D.C. volts applied through the .resistance 1,14 of potentiometer 11'4/115 and an arith metio average speed of 50 miles per hour, represented on a voltage scale of 0 to +510 volts equal to 0 to 100 miles per hour, the arm 115 will be positioned at` the 1/2 position interim the ends of the resistance 114. 'Thus 5 volts or 1/2 the applied voltage of 10'volts will be picked oi the resistance 114 by arm 115 and will represent the arithmetic average speed of 50 miles per hour. The 5 volts at arm 115 will be applied through the resistance 152 of potentiometer 151/152 to ground. The arm 151 which is positioned on the resistance 152 corresponding to the position of arm 115 on resistance 114, ywill also be positioned at the 1/2 position intermediate the ends of resistance 152. Thus with 5,volts applied through resistance 152 from arm 115, the voltage at arm 151 will be 1/2 the applied voltage of 5 volts or 2.5 volts above 1?' ground and will be the equal to 1A of the entire original input voltage of +10 volts and will be equal to the square of the fraction of the position of the arm 115, the square of 1/2 which is (1A).

With the voltage at arm 151 representing the arithmetic average speed squared, :1.5.2, the voltage is applied via lead 155 to FIG. 3a to resistances 156 and 157 to contact 155 of chopper 159.

The resistors 156 and 157 and chopper 159 are part of the subtracting circuit illustrated in block form in FIG. 1 and labeled 43.

The voltage representing the root mean square speed squared, R.M.S.'", is applied to lead 36 from the speed averaging unit and was determined from the same number of cars as the arithmeti-c average speed squared (M2) the number of cars being determined by the setting of arm 121 of adjustable resistance 120. rl`he voltage representing the BALS? is fed via lead 36 through resistance 164 and 165 to contact 161 of chopper 1519.

Since the root mean square speed squared, RMS?, value represents an average value of the squared speeds and the arithmetic average speed squared M2, value represents the squared average of the speeds, and both the root mean square (KMS.) value and the arithmetic average (AA.) value are based on the same vehicle speeds, it may be assumed that the Bah/1.5.2 value will be higher than the m2 value to the extent that there is any differences in the speeds of the cars from which the measurement is taken.

The di erence voltage between the R.M.S.2 value and the m2 value will be sensed at the capacitor 166 as the moving contact 162 of chopper 159 alternately connects between contacts 158 and 161. The diierence voltage in the form of an A.C. will pass through capacitor 166 and through resistance 157 to junction 163.

The A.C. voltage applied to junction 163 from chopper 159 is opposed by an A.C. voltage applied to junction 168 via resistor 169 from moving contact 173 o chopper 175.

rlhe A.C. voltage passed by moving contact 173 is the dierence voltage between the potential at contact 176, and the potential value at contact 174. The voltage at Contact 176 is essentially at Zero, with respect to ground, which zero potential is obtained by adjustment of arm 17S on the potential divider network 177 between a positive DC. of the order of +155 volts and a negative D.C. of l5 volts, for example, with ground connected in the network.

The voltage at contact 1741 is applied from the arm 135 of potentiometer 154/155 in PEG. v3b the deviation squared potentiometer, through lead 186 and resistor 179 and modiiied somewhat by the voltage divider circuit 137 to the contact 174 depending on the position o1 adjustable arm 11i-tl.

1t will be observed that of the two voltages applied to contacts of chopper 175 that applied to contact 176 is normally lower than that applied to contact 174 and of the two voltages applied to contacts of chopper 159 that applied to contact 161 is normally higher than that applied to Contact 158; and that the moving contacts 173 and 162 will operate in unison and connect respectively with contacts 176 and 161 at the same time. Thus the potentials applied to junction 165 will be 180 out of phase with each other and when the A.C. voltages at the moving contacts 173 and 16?. are substantially or" the same amplitude the potential at junction 168 will be substantially zero since the two applied A.C. potentials are equal and opposite and effectively cancel each other.

When the two A.C. voltages are unequal in amplitude an A.C. signal equal in amplitude to the difference in magnitude of the two voltages is passed through capacitor 18S to the grid of the power amplilier 189. The signal output of tube is ampliiied successively by t-riodes 1% and 194 and the amplified output is applied ,through coupling capacitor 195 and fed through coil k1% 18 to ground. Induced current in the other coil 197, of the couplin 7 transformer provides a potential to the grids 20'1 and 267 of beam power tubes 2.1M and 208 respectively. These tubes are connected for push-pull power amplification. i

'The preamplifier and two stage servo amplifier section are arranged for high gain amplification to provide for amplification of very small amplitudes of A.C. at junction so that very small diierences between the A.C.v at chopper 173 and the A.C. at chopper 159 may be sensed and amplilied. Therefore with such high gain amplification an A.C. of a relatively large amplitude at junction 16S may produce an excessively strong signal induced in coil 197. The diodes 215 and 211 are provided to reduce any excessively strong signal to a maximum limit so as to prevent overdriving of the amplifier output stage.

Since the choppers 175 and 153 are operated by the same A.C. power, the electrical phase of the A.C. potential at junction 168 and the phase of the A.C. operating the choppers 175 and 155 determines the direction of drive of the motor 223 in FlG. 3b in a similar manner as that described for directional control of the motor 144 with respect to the relation between the A.C. at capacitor 113 and the A.C. operating chopper 108.

The plate circuit of the tube 264 includes lead 214 to FIG. 3b, to the lower tap of coil 216 to the center tap of coil 216, lead 217 to the B-isupply. The cathode of tube 20K-.- is connected to ground via resistance 205.

"l" he plate circuit of the tube 20S includes lead 218 to FiG. 3b, to the upper tap of coil 216 to the center tap of coil 216, lead 217 to B+ supply. The cathode of tube is connected to ground via resistance 205.

The A.C. in coil 225' is an A.C. substantially in phase with the A.C. operating the choppers 175 and 158, and the A.C. in the coil 216 is related in phase to the A.C. at junction 165. Thus according to the phase relationship between the in coil 220 and the A.C. in coil 216 the servo motor 223 will be caused to rotate either clockwise or countercloclcwise. An indicator lamp L2, which is connected across the coil 216 is illuminated when the motor 223 is operating.

The arm of the potentiometer 154/185 is suitably geared to the motor 223 so that the arm 185 is positioned on the resistance 154 so that the voltage at arm 135, which is applied via lead 186 to FiG. 3a, through resistor 179 to contact 174, may be above ground zero, in a positive direction, the same amplitude as the magnitude of the difierence between the two voltages applied to contacts 155 and 161 of chopper 159. i

The arm 185 may be mechanically connected to arm 225 so that arm 22.5 is positioned on the resistor 224 of potentiometer 22d/225 corresponding to the position of arm 185 on the resistor 184. Y

This arrangement is similar to the arrangement of the potentiometers 114/ 115 and 151/152 and their associated DC. supply. As vfor example, a DC. supply of substantially the Vsame amplitude, +10 volts, is `applied through resistorv 224 and the voltage at arm 225 is applied through resistor 184. With the positions of arms 225 and 1,85 corresponding to each other the `fraction of the voltage at arm 155, rela-tive to the entire applied voltage (+10 volts), -is equal to the square of the fractional position of the -arrn 225 relative to its position on the resistor 224. Thus the potentiometer 1841/185 may be considered the deviation squared mechanical storage and potentiometer 224/225 may be considered the square root of deviation squared yor deviation mechanical lstorage with the output voltage at arm 225 via lead 230 corresponding to deviation.

Thus the arithmetic aver-age speed squared (m2) of a predetermined number of vehicle speeds is subtracted from the root metan square speed squared (R.M.S.2) of substantially t-he same vehicle speeds in a chopper 159. The result of the subtraction, a voltage representing the passes current.

remainder which is the square of the speed deviation, is

ksnatched by the output of a second chopper 175, the out- -put of chopper 175 being referenced to a desired zero approximating ground. The magnitude of the output of chopper 175 above zero, is representative of the voltage at arm 185 of squaring potentiometer 1184/185. The

square root of Ithe value at arm 155 is represented at arm `225. Therefore speed deviation, which is the square root of'the remainder of the subs-traction of AA? from the RJVLSZ is represented by the output voltage at arm 225 'which 'output may be applied via lead 239 to a meter 235 so that the voltage output representing deviation may be Iapplied to such grid. In the plate circuit of tube 235 is a relay 236 which may -be energized when tube 235 Adjustable cathode bias of tube 235 is provided so that the tube may provide current to energize the relay only above a certain value of deviation, as desired.

At and above certain values of deviation, as adjusted "by adjustment of the cathode bias, the tube 235 will pass current causing energization of relay 236 which relay will vthen close its normally open `contact 237 which may cornplete a circuit to do Work or operate an alarm, as desired. The output at arm 115, the arithmetic average speed may be applied to -a meter 228 or to ya terminal 228g.

Thus on meter 223 one may read the arithmetic average speed and on meter 232 one may read the speed deviation. InV FIG. 3b the adjustable resistance 120 is provided Vso that selection maybe made to average various number of vehicles through changing the position of selector switch 121.

'In FIG. 3a a potential divider 187 `is provided with adjustable selector 190 to provide selection of 4a percentage of the signal applied contact 174 of chopper 175. This provides for selection of difference calibration on the meter 232.

Considering the foregoing specification `and accompany ,ing drawings, 4alternate forms of the present invention have been presented thus accomplishing the stated and other objects. Obviously other modications, substitutions and rearrangement of parts may ybe resorted to without departing from :the spirit of the invention.

I claim:

l. A traffic speed deviation computer including means for sensing the individual speeds yof a series of vehicles having variable speed and variable time spacing, first means for providing a iirst -output representing the square of the root mean square of such speeds sensed by said sensing means irrespective of variation in time spacing between successive individual speeds, said first means including means for varying the value of the rst output ,in proportion to the diierence between said first output and each particular speed signal and in proportion :to a predetermined number of such vehicles, yand second means for providing a second output representing the square of .the arithmetic average of such speeds sensed by said sensing means irrespective of variation in time spacing between successive individual speeds, said second means including means for varying the value of the second output in proportion to the dierence between said second outfor receiving said rst and second outputs and deriving `therefrom an output representing the dierence between said Iiirst and second outputs, and means for deriving the square root of said difference output to provide an output representing the average deviation of the sensed speeds from the average of said predetermined number sensed speeds.

2. A traic speed deviation computer as in claim 1 and hicles successively passing a point along a roadway, means for providing a iirst electricm output representing the square of the root mean square of such speeds of a predetermined number of vehicles having most recently passed s-aid ypoint and sensed by said sensing means irrespective of variation in time spacing between successive individual speeds, means for providing a second electrical output representing the square of the arithmetic average of such speeds of said most recently passed predetermined nurnber of vehicles sensed by said sensing means irrespective of variation in time spacing between successive individual speeds, means for receiving said first and second outputs and continuously deriving therefrom an output representing the dilierence between said first and second outputs.

5. A tratiic speed deviation computer including means -for continuously sensing the speeds of a series of vehicles and developing therefrom an electrical signal representing the squared root mean square of such speeds, means for continuously sensing the speeds of said series of vehicles and providing another electrical signal representing the square of the arithmetic average of such speeds, means for storing each of said electrical values, said means providing electrical signals representing the squared root means square and squared `arithmetic average of such speeds including means for varying its individual stored value in proportion to a predetermined number of vehicles, means -for continuously sensing the difference between said st-ored electrical signals to provide an electrical signal representing the square of the deviation of such speeds and means for deriving the square root of the last named signal to provide an output representing the deviation of such speeds.

6. A traiiic speed deviation computer as in claim 5 and in which said last named output is an electrical value and said computer includes a meter for indicating said electrical value in terms of deviation of speed.

7. A system for continually computing the root mean square deviation of a continually varying series of a predetermined number or" speed values representing the speeds of a continually varying series of vehicles in tr-atiic, incuding means for receiving said speed values and determining a mean square average of said values and providing an electrical output representing said average, means for receiving said same speed values and determining an arithmetic average of said values and providing an electrical output representing the last named average, means for squaring said last named 4average output, means for continually comparing said squared last named average output with said mean square average output to continually derive an electrical output representing the diterence between said average Outputs, means for deriving fthe square root of the last named electrical output -to provide an output representing said deviation.

8. A system `as in claim 7 :and including means for adjusting said averaging means to vary said predetermined number of vehicles and corresponding number of received speed values for such averaging.

9. A system as in claim 8 in which said adjusting means are cooperatively adjusted for the respective squared average and average square signals whereby the last named signals will be averaged on corresponding numbers of vehicles.

l0. A Isystem las in claim 7 in which said means for providing said squared average and average square signals are recycled in response Ito each new received speed value -to readjust the last two named signals for each said new 21 received speed value whereby `said deviation output will be substantially continuously adjusted for the latest desired number of vehicles.

11. A system as in yclaim 7 and including means for adjusting the deviation output in relation to the received speed value.

12. In a system for determining the average devia-tion of a number of values from an -average of such values land having means for sensing the individual values in succession and developing therefrom electrical signals representing each latest individual value and the lsquare of the root mean square of the latest predetermined number of said values respectively irrespective of variation in time spacing between successive individual val-ues, the combination of means for receiving each said latest individual value and -developing an electrical signal representing the square of the arithmetic average yof said latest predetermined number of values irrespective of variation in time spacing between successive individual values, means for comparing said squared root mean square electrical signal and said squared arithmetic average electrical signal to derive a further electrical signal representing thedifference between the compared signals, and means for developing from said further signal ian electrical output signal representing the square root of said difference signal to represent said deviation.

13. A combination as in claim l2 in which said comparing means includes a chopper having alternate inputs connected to the respective compared signals land an output alternating between said inputs, Iand a capacitor in series with said output t-o provide an alternating current `output therefrom, and means controlled by said alternating current output for providing said fur-ther electrical signal.

14. A combination as in claim l2 and in which said comparing means includes a chopper having two inputs connected to the respective compared signals and an output alternately connected to its respective inputs and a capacitor in series with its output, and in which said square root deriving means includes two potentiometers having stationary resistance elements and contact arms mechanically linked to be movable together over the respective resistance elements, the resistance element of one of said potentiometers being connected across a predetermined direct current voltage and the other resistance element being connected between the arrn of said one potentiometer and one end of its resistance element, a second chopper having two inputs one of which is connected to the arm of the second of said potentiometers and the other input of which is connected to a reference `direct current voltage for ysetting zero reference with respect to the output voltage on the last named contact arm, and said chopper having an output alternately connected to its respective inputs, a servo-amplifier having an input and output, impedance means interconnecting the outputs of the respective choppers to provide an alternating current input to said servo-amplifier of amplitude substantially proportional to the difference between the outputs of said choppers and ywhose phase reverses for reversal of relative amplitude of the outputs of said choppers, and a servomotor controlled by said servo-amplifier to move said Contact arms so that the output voltage of the arm of said other potentiometer with respect to the zero reference corresponds with the output of the iirst chopper and thus to the diierence between the average squared signal and the `squared average signal and thus to the square of the deviation, and the output of the arm of the said one potentiometer represents the square root of said difference and thus the deviation.

15. In a system Ifor determining the deviation of the latest predetermined number of a continuing random spaced series of varied electrical values, means for receiving each said value and initiating a computing cycle therefrom, means for storing the latest said value in said cycle in place of the previous said value, and providing an electrical output therefrom, means for squaring said latest value and storing said squared value in said cycle, means for storing the average of the squares of the latest predetermined number of isaid values from the previous said cycle, means for readjusting said stored squared average by a fraction of the difference between the previous stored squared average value and the latest stored squared individual such value based on the said predetermined number to provide and store the new latest squared average of the values, means for ldeveloping and storing an arithmetic average of said latest predetermined number of individual values `and which said arithmetic average is readjusted by a fraction of the difference between the previous stored arithmetic average and the new latest individual stored value, means for squaring said stored arithmetic average and storing said squared average to complete the cycle, means for comparing the two stored squared averages to derive and store .the difference between them as the square of `the deviation, and means for deriving and storing the square root of the last named difference as representing the deviation.

16. Electrical apparatus for substantially continuously determining the root mean square deviation of speeds of vehicles proceeding past a given location along a traflic lane having variable speed and variable time spacing, including means for sensing the individual speeds of said vehicles, means for deriving from the speeds s0 sensed a first electrical signal representing the square of the root mean 4square of the speeds of the latest predetermined number of said vehicles, means for deriving -from the speeds so sensed a second electrical signal representing the square of the arithmetic average of the same latest predetermined number of said vehicles, means for deriving from said first and second signals a third electrical ysignal representing `the difference between said first and second signals, and means for deriving from said third signal an output signal representing the square root of said third signal, whereby the last named output signal will represent said deviation of speeds for said latest predetermined number of vehicles.

17. A traic lspeed deviation computer including means `for continuous sensing of the individual speeds of each of the successive vehicles passing a point along a roadway, means for providing a first electrical output continuously representing the square of the root mean square of the `speeds of a group of vehicles most recently having passed said sensing point, means for providing a second electrical output representing the square of `the arithmetic average of the speeds of said most recent vehicles, means for deriving an output continuously representing the difference between lsaid first and second output signals, and means for deriving the square root of said difference signal to provide an output representing average vehicle speed deviation.

18. A combination as in claim 17 in which said squared root mean square and arithmetic averaging means include means for varying their output in response to each vehicle inversely in proportion to the number of vehicles desired to be averaged.

19. A combination as in claim 17 in which said averaging means include means for averaging over an adjustable number of vehicles.

20. A combination as in claim 17 in which at least one of said averaging circuits includes a servo motor, servo amplifier, chopper and potentiometers connected to derive the potentiometer to balance at a null point and to derive the squared function from the tap on one of the potentiometers.

Rey et al. Apr. 23, 1957 Radley et al. Dec. 20, 1960 

1. A TRAFFIC SPEED DEVIATION COMPUTER INCLUDING MEANS FOR SENSING THE INDIVIDUAL SPEEDS OF A SERIES OF VEHICLES HAVING VARIABLE SPEED AND VARIABLE TIME SPACING, FIRST MEANS FOR PROVIDING A FIRST OUTPUT REPRESENTING THE SQUARE OF THE ROOT MEANS SQUARE OF SUCH SPEEDS SENSED BY SAID SENSING MEANS IRRESPECTIVE OF VARIATION IN TIME SPACING BETWEEN SUCCESSIVE INDIVIDUAL SPEEDS, SAID FIRST MEANS INCLUDING MEANS FOR VARYING THE VALUE OF THE FIRST OUTPUT IN PROPORTION TO THE DIFFERENCE BETWEEN SAID FIRST OUTPUT AND EACH PARTICULAR SPEED SIGNAL AND IN PROPORTION TO A PREDETERMINED NUMBER OF SUCH VEHICLES, AND SECOND MEANS FOR PROVIDING A SECOND OUTPUT REPRESENTING THE SQUARE OF THE ARITHMETIC AVERAGE OF SUCH SPEEDS SENSED BY SAID SENSING MEANS IRRESPECTIVE OF VARIATION IN TIME SPACING BETWEEN SUCCESSIVE INDIVIDUAL SPEEDS, SAID SECOND MEANS INCLUDING MEANS FOR VARYING THE VALUE OF THE SECOND OUTPUT IN PROPORTION TO THE DIFFERENCE BETWEEN SAID SECOND OUTPUT AND EACH PARTICULAR SPEED SIGNAL AND IN PROPORTION TO SAID PREDETERMINED NUMBER OF SUCH VEHICLES, MEANS FOR RECEIVING SAID FIRST AND SECOND OUTPUTS AND DERIVING THEREFROM AN OUTPUT REPRESENTING THE DIFFERENCE BETWEEN SAID FIRST AND SECOND OUTPUTS, AND MEANS FOR DERIVING THE SQUARE ROOT OF SAID DIFFERENCE OUTPUT TO PROVIDE AN OUTPUT REPRESENTING THE AVERAGE DEVIATION OF THE SENSED SPEEDS FROM THE AVERAGE OF SAID PREDETERMINED NUMBER SENSED SPEEDS. 